New study hints that we’re closing in on metallic hydrogen

Scientific Method / Science & Exploration

http://arstechnica.com/

It's taken 80 years, but high pressure may be breaking down hydrogen molecules.

by John Timmer - Jan 6, 2016 1:30pm CST

Raman spectroscopy and a diamond anvil were used to identify 

and characterize a new phase of hydrogen. Philip Dalladay-Simpson

and Eugene Gregoryanz

We tend to think of the properties of the chemical elements as immutable—a metal is a metal, and a gas is a gas. But all those properties are what we experience on Earth. The Universe, on the other hand, is filled with extremes of temperature and pressure that cause elements to defy our expectations. Pluto is covered in nitrogen ice, while some exoplanets are likely to experience rains of liquid metal.

Further Reading

Strange, unpredictable chemistry at high pressure

Extreme pressure has "a completely different atomic table," vital to understanding space.

Close to the cores of gas giants, elements are squeezed by unimaginable pressures, capable of rearranging electron orbitals and playing havoc with the chemical bonding we see on Earth. Here, theorists have predicted, the electrons of hydrogen could be set free, converting the gas into a solid or liquid metal. But while researchers first predicted the existence of metallic hydrogen 80 years ago, the element has stubbornly refused to appear, even after we've raised pressures well above where it was expected to appear.
Now, three Edinburgh-based researchers report placing hydrogen under the highest pressures yet achieved. Scans of the resulting material suggest that the chemical bonds that normally link hydrogen into a molecule are starting to break down, heralding the possible appearance of a metallic form.
Like other high-pressure work, the new experiments rely on what are called diamond anvils, which use two diamonds to crush any material placed between them. This hardware can apply absurd pressure to samples. For the experiments reported here, the material being crushed reached pressures of over 380 GigaPascals—with each GigaPascal being roughly equivalent to 10,000 atmospheres of pressure. These are the highest pressures achieved with hydrogen and among the highest pressures ever reported.
(The researchers tested both hydrogen and its heavier isotope, deuterium, as well as a mixture of the two isotopes.)
Normally, hydrogen comes in a molecular form, with two atoms sharing their electrons. This bond keeps the electrons from circulating freely and determines many of the molecule's properties. These properties include things like the wavelengths of light it absorbs as the electrons change their energy levels or the bond between them stretches. Making a metal involves dissolving that bond and therefore changing the properties.
Under visible light, hydrogen is normally transparent—it doesn't absorb any of these wavelengths. But that changed under extreme pressure, which the authors took as a possible sign that the bonding was breaking down: "The possible appearance of conducting electrons due to dissociation could explain the very dark appearance of the sample as seen in transmitted and reflected light in the visible region."
They also used Raman spectroscopy to look at the behavior of the bond, as this can provide information on its vibrations. At these pressures, two modes of vibration present in hydrogen molecules start to disappear, and the intensities of the remaining vibrational modes begin to decrease rapidly.
Since some signs of a bond are still present, the authors posit that this represents a new phase of hydrogen accompanying the gas and more readily achieved liquid forms. Because of some other exotic phases discovered in the search for hydrogen metal, this one is named phase V. The authors don't think that it represents a fully metallic form, since there are some signs that the bonds between hydrogen atoms are still present. But they're clearly not as robust as they were, so the authors speculate that it represents "the onset of the predicted non-molecular and metallic state of hydrogen."
The researchers also change the temperature of the sample and show that the boundaries between this new phase and phase IV are purely pressure-based—it doesn't seem to matter what the temperature is; the transition takes place at about 320 GigaPascals. This was taken as evidence that raising the temperature might create a form of hydrogen that's essentially a liquid metal.
The very weak signs of a chemical bond that remain suggest that it may only take a bit more pressure to get fully metallic hydrogen. But given the history of the field, I'd imagine many people will believe it when they see it.
Nature, 2015. DOI: 10.1038/nature16164  (About DOIs).

Stainless magnesium could be mass produced and it would weigh half as much as aluminum

Researchers led by a team at UNSW Australia have used the Australian Synchrotron to turn the discovery of an ultra-low density and corrosion-resistant magnesium alloy into the first step toward mass-producing ‘stainless magnesium’, a new high-strength, lightweight metal, paving the way for cars, trucks and aeroplanes that can travel further distances on less petrol.

The magnesium-lithium alloy weighs half as much as aluminium and is 30 per cent lighter than magnesium, making it an attractive candidate to replace these commonly used metals to improve fuel efficiency and greatly reduce greenhouse gas emissions from transport vehicles.

Australian researchers formed a protective surface layer for magnesium that can be considered similar to the way a layer of chromium oxide enables the protection of stainless steel.

‘Many similar alloys have been created as researchers seek to combine the incredible lightness of lithium with the strength and durability of magnesium to develop a new metal that will boost the fuel efficiency and distance capacity of aeroplanes, cars and spacecraft.

‘This is the first magnesium-lithium alloy to stop corrosion from irreversibly eating into the alloy, as the balance of elements interacts with ambient air to form a surface layer which, even if scraped off repeatedly, rapidly reforms to create reliable and durable protection.’

Professor Ferry, senior author of the paper led by Dr Wanqiang Xu also from UNSW, says this excellent corrosion resistance was observed by chance, when his team noticed a heat-treated sample from Chinese aluminium-production giant, CHALCO, sitting, inert, in a beaker of water.

‘To see no corroded surfaces was perplexing and, by partnering with scientists on the Powder Diffraction (PD) beamline at the Australian Synchrotron, we found the alloy contains a unique nanostructure that enables the formation of a protective surface film.

‘Now we’ve turned our attention to investigating the molecular composition of the underlying alloy and the carbonate-rich surface film, to understand how the corrosion process is impeded in this “stainless magnesium”.’

The transport sector accounts for 90 megatonnes (90 billion kilograms) of greenhouse gas emissions in Australia each year, or 16 per cent of Australia’s total; road vehicles account for 77 megatonnes and aviation eight tonnes.

They plan incorporate new techniques into the mass-production of this unique alloy in sheets of varying thickness, in a standard processing plan. Stainless magnesium could be as durable as steel but far lighter.

Nature Materials - A high-specific-strength and corrosion-resistant magnesium alloy

Abstract

Ultra-lightweight alloys with high strength, ductility and corrosion resistance are desirable for applications in the automotive, aerospace, defence, biomedical, sporting and electronic goods sectors. Ductility and corrosion resistance are generally inversely correlated with strength, making it difficult to optimize all three simultaneously. Here we design an ultralow density (1.4 g cm−3) Mg–Li-based alloy that is strong, ductile, and more corrosion resistant than Mg-based alloys reported so far. The alloy is Li-rich and a solute nanostructure within a body-centred cubic matrix is achieved by a series of extrusion, heat-treatment and rolling processes. Corrosion resistance from the environment is believed to occur by a uniform lithium carbonate film in which surface coverage is much greater than in traditional hexagonal close-packed Mg-based alloys, explaining the superior corrosion resistance of the alloy.

Super strong, lightweight metal could build tomorrow's spacecraft

"Our method paves a new way to enhance the performance of many different kinds of metals," said engineer Xiaochun Li.

By Brooks Hays   |   Dec. 24, 2015 at 10:27 AM

6 Comments

A close-up image shows magnesium before and after the introduction of ceramic nanoparticles. Photo by UCLA/Li

LOS ANGELES, Dec. 24 (UPI) -- A new metal, a combination of magnesium and ceramic silicon carbide nanoparticles, is promising to change how airplanes, spacecraft and cars are manufactured.
Its inventors, materials scientists at UCLA, say the metal is super strong, but most importantly, lightweight. The metal's stiffness-to-weight ratio is what sets it apart from similar inventions.
Researchers say the metal may be just the first of many groundbreaking manufacturing materials. That's because they've invented a new technique for infusing metals without nanoparticles without hurting the metal's structural integrity.
"It's been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now," researcher Xiaochun Li, a professor of manufacturing and engineering at UCLA, said in a press release.
"With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today's society."
After processing, researchers tested the magnesium, newly infused with a dense, even spread of nanoparticles. The new material showed improved strength, stiffness, plasticity and durability under high temperatures.
Previous research showed ceramic nanoparticles have a tendency to clump together when added to metals, making them stronger but weakening their plasticity. Researchers solved this problem by dispersing the nanoparticles in a molten magnesium zinc alloy.
Because magnesium is relatively abundant and the production technology can be easily scaled up, scientists hope the metal's industrial applications will be quickly realized. And scientists don't think it will be long before they've found a new metal-nanoparticle combination with impressive potential.
"The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities," Li said.
The new metal nanocomposite is detailed in the jouranl Nature.

Cobalt atoms on graphene a powerful combo

http://nextbigfuture.com/

October 25, 2015

Graphene doped with nitrogen and augmented with cobalt atoms has proven to be an effective, durable catalyst for the production of hydrogen from water, according to scientists at Rice University.

The Rice lab of chemist James Tour and colleagues at the Chinese Academy of Sciences, the University of Texas at San Antonio and the University of Houston have reported the development of a robust, solid-state catalyst that shows promise to replace expensive platinum for hydrogen generation.

A new catalyst just 15 microns thick has proven nearly as effective as platinum-based

 catalysts but at a much lower cost, according to scientists at Rice University. The 

catalyst is made of nitrogen-doped graphene with individual cobalt atoms that activate

 the process. (Credit: Tour Group/Rice University)

Nature Communications - Atomic cobalt on nitrogen-doped graphene for hydrogen generation



Catalysts can split water into its constituent hydrogen and oxygen atoms, a process required for fuel cells. The latest discovery, detailed in Nature Communications, is a significant step toward lower-cost catalysts for energy production, according to the researchers.

“What’s unique about this paper is that we show not the use of metal particles, not the use of metal nanoparticles, but the use of atoms,” Tour said. “The particles doing this chemistry are as small as you can possibly get.”

Even particles on the nanoscale work only at the surface, he said. “There are so many atoms inside the nanoparticle that never do anything. But in our process the atoms driving catalysis have no metal atoms next to them. We’re getting away with very little cobalt to make a catalyst that nearly matches the best platinum catalysts.” In comparison tests, he said the new material nearly matched platinum’s efficiency to begin reacting at a low onset voltage, the amount of electricity it needs to begin separating water into hydrogen and oxygen.

The new catalyst is mixed as a solution and can be reduced to a paper-like material or used as a surface coating. Tour said single-atom catalysts have been realized in liquids, but rarely on a surface. “This way we can build electrodes out of it,” he said. “It should be easy to integrate into devices.”

The researchers discovered that heat-treating graphene oxide and small amounts of cobalt salts in a gaseous environment forced individual cobalt atoms to bind to the material.

Electron microscope images showed cobalt atoms widely dispersed throughout the samples.

They tested nitrogen-doped graphene on its own and found it lacked the ability to kick the catalytic process into gear. But adding cobalt in very small amounts significantly increased its ability to split acidic or basic water.

“This is an extremely high-performance material,” Tour said. He noted platinum-carbon catalysts still boast the lowest onset voltage. “No question, they’re the best. But this is very close to it and much easier to produce and hundreds of times less expensive.”

Atom-thick graphene is the ideal substrate, Tour said, because of its high surface area, stability in harsh operating conditions and high conductivity. Samples of the new catalyst showed a negligible decrease in activity after 10 hours of accelerated degradation studies in the lab.

Abstract

Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts.

Author: brian wang on 10/25/2015

http://www.gizmag.com/

High-efficiency, semi-transparent perovskite/graphene solar cells created at low cost

• Colin Jeffrey
• September 11, 2015

The semi-transparent, inexpensive solar cells have a claimed
conversion efficiency of around 12 percent
 (Credit: Hong Kong Polytechnic University)

With the continued rise in the uptake of solar cells, consumers are now looking at less obtrusive ways to incorporate these in buildings and vehicles. Transparent or semi-transparent cells provide greater flexibility and visual appeal than standard, opaque silicon solar cells, however their relatively high-cost and poor efficiencies have meant that their adoption has been slow. To help remedy this, researchers working at the Hong Kong Polytechnic University (PolyU) have created semi-transparent, efficient, low-cost perovskite solar cells with graphene electrodes.
First generation silicon solar cells have been the mainstay of photovoltaic (PV) energy conversion for many years now due to their high stability and efficient energy conversion, but their opacity and expense mean that alternatives are now being actively sought for modern building and vehicle applications. Thin film PVs (second generation solar cells) are lightweight and flexible, but are expensive because they are created from rare materials using complex structures requiring high-temperature production processes.
Now, utilizing such materials as thin-film perovskite, the third generation of solar cell is currently being developed for commercial use in the not-too-distant future with the promise of greater power conversion efficiencies, simpler fabrication processes, and lower cost.
In this vein, the PolyU researchers have developed their own version of the third generation solar cell using semitransparent perovskite with graphene used as the electrodes. Being exceptionally thin but with high conductivity and low cost, graphene makes an ideal choice for semitransparent solar cells as it allows light to be absorbed from both sides. As such, the researchers envisage these devices potentially able to be used in windows, louvers, and building roof surfaces, thereby increasing the available surface area for collecting solar energy.

With a claimed power conversion efficiency of around 12 percent, the PolyU solar cells outperform standard transparent and semi-transparent versions hands-down. The potential to be produced at less than HK $0.50 (US $0.06)/Watt also means a greater than 50 percent saving on the cost of conventional silicon solar cells.
While graphene has been around for more than a decade now and is highly-efficient as a conductor in its own right, the PolyU researchers decided to further enhance the conductivity of graphene to meet their specific requirements. To do this, the graphene was coated with a patina of PEDOT:PSS conductive polymer (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) – the same ingredient recently used by KAIST scientists in the production of weavable LED fibers – that also acted as an adhesion layer to the perovskite during the process of lamination.
To promote power conversion efficiency, the researchers found that by multilayering graphene through chemical vapor deposition to create transparent electrodes, the sheet resistance of the electrodes was additionally reduced while the exceptional transparency of the electrodes was retained. Finally, the performance of the device was further improved by enhancing the degree of contact between the top graphene electrodes and the hole transport layer on the perovskite film.
According to the researchers, the exceptional flexibility of graphene and the simplified preparation of the cells means that the PolyU device could be eminently suitable for mass production via direct printing or using a roll-to-roll process. In this way, semitransparent solar cells may well provide a greater uptake of PV panels across markets not currently serviced by traditional, opaque devices.
The results of this research were published in the journal Advanced Materials.
Source: Hong Kong Polytechnic University

http://nextbigfuture.com/

September 29, 2015

Galfenol can convert 70 percent of an applied mechanical energy into magnetic energy

An alloy first made nearly two decades ago by the U. S. Navy could provide an efficient new way to produce electricity. The material, dubbed Galfenol, consists of iron doped with the metal gallium. In new experiments, researchers from UCLA, the University of North Texas (UNT), and the Air Force Research Laboratories have shown that Galfenol can generate as much as 80 megawatts of instantaneous power per square meter under strong impacts.

Galfenol converts energy with high efficiency; it is able to turn roughly 70 percent of an applied mechanical energy into magnetic energy, and vice versa. (A standard car, by contrast, converts only about 15 to 30 percent of the stored energy in gasoline into useful motion.) Significantly, the magnetoelastic effect can be used to generate electricity. "If we wrap some wires around the material, we can generate an electrical current in the wire due to a change in magnetization," Domann said.

Galfenol in experiments using a device called a Split-Hopkinson Pressure Bar to generate high amounts of compressive stress (e.g., powerful impacts). They found that when subjected to impacts, Galfenol generates as much as 80 megawatts of instantaneous power per cubic meter.

By way of comparison, a device known as an explosively driven ferromagnetic pulse generator produces 500 megawatts of power per cubic meter. However, as their name implies, such generators require an explosion—one that destroys the ferromagnet, even as it produces power.

Among the potential applications, Galfenol-powered devices could be used as wireless impact detectors. "Essentially, we could fabricate small devices that send out a detectable electromagnetic wave when a mechanical pulse moves through it," Domann said. These devices could be embedded in vehicles—military or civilian—to detect collisions. Because electromagnetic waves travel three orders of magnitude faster than mechanical waves, information about the impact could be transmitted ahead of the waves created by the impact.

This picture is of the experimental setup showing the Hopkinson bar

 surrounded by a water-cooled electromagnet. A cylinder of Galfenol

 is inside of the electromagnet, sandwiched between the Hopkinson bars.

 The magnet was used to apply a wide range of static magnetic fields to

 Galfenol while it was mechanically impacted. Credit: John Domann/UCLA

Journal of Applied Physics - High strain-rate magnetoelasticity in Galfen

This paper presents the experimental measurements of a highly magnetoelastic material (Galfenol) under impact loading. A Split-Hopkinson Pressure Bar was used to generate compressive stress up to 275 MPa at strain rates of either 20/s or 33/s while measuring the stress-strain response and change in magnetic flux density due to magnetoelastic coupling. The average Young's modulus (44.85 GPa) was invariant to strain rate, with instantaneous stiffness ranging from 25 to 55 GPa. A lumped parameters model simulated the measured pickup coil voltages in response to an applied stress pulse. Fitting the model to the experimental data provided the average piezomagnetic coefficient and relative permeability as functions of field strength. The model suggests magnetoelastic coupling is primarily insensitive to strain rates as high as 33/s. Additionally, the lumped parameters model was used to investigate magnetoelastic transducers as potential pulsed power sources. Results show that Galfenol can generate large quantities of instantaneous power (80 MW/m3 ), comparable to explosively driven ferromagnetic pulse generators (500 MW/m3 ). However, this process is much more efficient and can be cyclically carried out in the linear elastic range of the material, in stark contrast with explosively driven pulsed power generators.

A Kolsky bar was used to generate large constant strain rates in Galfenol, and measure the stress-strain response, as well as the change in magnetic flux density due to magnetoelastic coupling. The experimental results indicate that the average Young's modulus of Galfenol is invariant with increasing strain rates of up to 33/s. The measured voltage was proportional to strain rate, with a more rounded appearance, attributed to dynamic magnetic effects. Furthermore, the measured voltage and change in flux were highly dependent on bias field strength. A lumped parameters model was created that effectively simulates the measured pickup coil voltages in response to an applied stress pulse. The model suggests that magnetoelastic coupling is relatively insensitive to strain rates as high as 33/s. The model also suggests that Galfenol can generate large quantities of instantaneous power, comparable to those created by explosively driven ferromagnetic pulse generators. However, this process is much more efficient and can be cyclically carried out in the linear elastic range of the material, in stark contrast with explosively driven pulsed power generators.

SOURCES- UCLA, Phys.org, Journal of Applied Physics 

 http://nextbigfuture.com/

September 29, 2015

Solar Cells Will be Made Obsolete by 3D rectennas aiming at 40-to-90% efficiency

A new kind of nanoscale rectenna (half antenna and half rectifier) can convert solar and infrared into electricity, plus be tuned to nearly any other frequency as a detector.

Right now efficiency is only one percent, but professor Baratunde Cola and colleagues at the Georgia Institute of Technology (Georgia Tech, Atlanta) convincingly argue that they can achieve 40 percent broad spectrum efficiency (double that of silicon and more even than multi-junction gallium arsenide) at a one-tenth of the cost of conventional solar cells (and with an upper limit of 90 percent efficiency for single wavelength conversion).

It is well suited for mass production, according to Cola. It works by growing fields of carbon nanotubes vertically, the length of which roughly matches the wavelength of the energy source (one micron for solar), capping the carbon nanotubes with an insulating dielectric (aluminum oxide on the tethered end of the nanotube bundles), then growing a low-work function metal (calcium/aluminum) on the dielectric and voila--a rectenna with a two electron-volt potential that collects sunlight and converts it to direct current (DC).

"Our process uses three simple steps: grow a large array of nanotube bundles vertically; coat one end with dielectric; then deposit another layer of metal," Cola told EE Times. "In effect we are using one end of the nanotube as a part of a super-fast metal-insulator-metal tunnel diode, making mass production potentially very inexpensive up to 10-times cheaper than crystalline silicon cells."

For commercialization, billions or even trillions of carbon-nanotube bundles could be grown side-by-side, ramping up the power output into the megaWatt range, after optimization for higher efficiency.

"We still have a lot of work to do to lower contact resistance which will improve the impedance match between the antenna and diode, thus raising efficiency," Cola told us."Our proof-of-concept was tuned to the near-infrared. We used infrared-, solar- and green laser-light and got efficiencies of less than one percent, but what was key to our demo was we showed our computer model matched our experimental results, giving us the confidence that we can improve the efficiency up to 40 percent in just a few years."

For the future, Cola's group has a three tiered goal--first develop sensor applications that don't require high efficiencies, second to get the efficiency to 20 percent for harvesting waste heat in the infrared spectrum, then start replacing standard solar cells with 40 percent efficient panels in the visible spectrum. The team is also seeking suitable flexible substrates for applications that require bending.

Schematic of the components making up the optical rectenna--carbon nanotubes 

 capped with a metal-oxide-metal tunneling diode. (Credit: Thomas Bougher)
(Source: Georgia Tech)

Nature Nanotechnology - A carbon nanotube optical rectenna

An optical rectenna—a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current—was first proposed over 40 years ago, yet this concept has not been demonstrated experimentally due to fabrication challenges at the nanoscale. Realizing an optical rectenna requires that an antenna be coupled to a diode that operates on the order of 1 pHz (switching speed on the order of 1 fs). Diodes operating at these frequencies are feasible if their capacitance is on the order of a few attofarads but they remain extremely difficult to fabricate and to reliably couple to a nanoscale antenna. Here we demonstrate an optical rectenna by engineering metal–insulator–metal tunnel diodes, with a junction capacitance of ∼2 aF, at the tip of vertically aligned multiwalled carbon nanotubes (∼10 nm in diameter), which act as the antenna. Upon irradiation with visible and infrared light, we measure a d.c. open-circuit voltage and a short-circuit current that appear to be due to a rectification process (we account for a very small but quantifiable contribution from thermal effects). In contrast to recent reports of photodetection based on hot electron decay in a plasmonic nanoscale antenna a coherent optical antenna field appears to be rectified directly in our devices, consistent with rectenna theory. Finally, power rectification is observed under simulated solar illumination, and there is no detectable change in diode performance after numerous current–voltage scans between 5 and 77 °C, indicating a potential for robust operation.

DARPA working on several approaches for new advanced materials

Harnessing radical new tools—from ultrafast laser imagers to groundbreaking chemical synthesis approaches—DARPA’s Defense Sciences Office (DSO) is aggressively pursuing the development of novel materials with the potential to boost national security.

One major challenge in developing new materials has been the difficulty of retaining and exploiting the unique characteristics that emerge in materials at the nanoscale (a few 10-billionths of a meter). Many materials demonstrate unique and potentially useful electrical, optical and tensile characteristics at these nearly atomic scales, but lose these traits when engineered into millimeter- or centimeter-scale products and systems. DSO’s Atoms to Product (A2P) program aims to cross that divide by developing assembly methods that allow the retention of desirable nanoscale properties in macro-scale materials, components and systems.

“In the past, scientists made most of their new materials through variants of ‘mix, heat and form,’” said DARPA program manager John Main. “Now we’re taking an entirely different approach, starting with individual atoms, assembling them into nano-structures, then assembling the nano-structures into larger micro-devices. A2P is taking advantage of new methods for controlling nanoscale assembly at very high throughputs to economically build novel micro-devices.”

DARPA is pursuing other approaches to creating new materials with unique properties through its Materials with Controlled Microstructural Architecture (MCMA) program. This program seeks to control the architecture of material microstructures to improve structural efficiency and realize properties that traditionally aren’t achieved together in a single substance, such as the strength of steel and the weight of plastic. The work could also help incorporate other important properties, such as high rates of heat diffusion for thermal management applications and tailorability of thermal expansion to enable joining of normally incompatible materials

One potential benefit of applying control over the internal, nano-architecture of materials is that the materials may then be able to catalyze reactions or perform energy conversions, effectively becoming devices in and of themselves. That’s precisely the goal of DSO’s Materials for Transduction (MATRIX) program. Like A2P, it aims to realize the beneficial properties of new materials at the device or system level—in this case by developing new materials for transduction, the conversion of energy from one form into another.

“Transduction is critical to countless military capabilities on land, under water, in the air and in space,” said DARPA program manager Jim Gimlett, pointing to such examples as communications antennas, which convert radio waves to electrical signals, and thermoelectric generators, which convert heat to electricity. But research efforts to develop new transductional materials have largely been limited to laboratory demonstrations and have too often failed to translate into functional devices and systems. MATRIX aims to make a difference by speeding the development of significant new capabilities and enabling size and weight reductions for existing military devices and systems.

DSO’s Extended Solids (XSolids) program takes aim at a different class of materials—those that currently can be made and exist only at ultrahigh pressures up to millions of times atmospheric pressure. Many materials subjected to these pressures exhibit dramatic improvements in their physical, mechanical and functional properties. These new “polymorphs” may provide significant performance enhancements in areas as diverse as semiconductor electronics and propulsion, and in structural applications ranging from aerospace to ground vehicles. “The discovery and fabrication of new materials has long been based on the application of heat,” said Goldwasser. “The development of high-pressure chemistry—or barochemistry—could open up a new era in materials discovery and development featuring an entirely new palette of materials for exploitation.”

Early work already hints at unique materials and properties that may emerge when everyday gasses such as carbon dioxide as well as silicon- and carbon-based solids are compressed under extreme conditions, Goldwasser noted. But because their synthesis and stabilization is so demanding, production of these materials for practical use has proven difficult. So in addition to materials discovery, XSolids is researching processing techniques to make their fabrication practical.

Recent scientific advances have opened up new possibilities for material design in the ultrahigh pressure regime (up to three million times higher than atmospheric pressure). Materials formed under ultrahigh pressure, known as extended solids, exhibit dramatic changes in physical, mechanical and functional properties and may offer significant improvements to armor, electronics, propulsion and munitions systems in any aerospace, ground or naval platform.

Despite the dramatic performance improvements—both demonstrated and predicted—for extended solids, the ultrahigh pressures currently required for synthesis and stabilization of such materials prevent scalability for any practical use. DARPA created the Extended Solids (XSolids) program to address the key challenges in synthesis and scale-up necessary for manufacture, through both computational and experimental approaches, with the intention of opening a vast new material design space for the DoD.

Interdisciplinary research teams are working to develop multi-step, barochemical processes that can reduce the peak pressure needed to achieve scalable synthesis of target materials. Performers are working in parallel on computational exploration of high-pressure material structures and properties, and the small-scale synthesis of a variety of materials to experimentally verify their properties.

While A2P, MATRIX and XSolids all address in various ways the challenge of scaling innovations from smaller to larger dimensions, another DSO materials program is addressing the challenge of how to add precision to the production of extremely thin films of substances. DSO’s Local Control of Materials Synthesis (LoCo) program seeks to advance thin-film materials and surface coatings, which are used in military applications ranging from optics to advanced electronics.

Nanolattices have the potential to increase strength to weight by one million times but massively scaling production is the main hurdle

February 26, 2015

If nanolattice material could be produced in large quantities, they could replace composites and other materials used in a wide range of applications, because they’d be just as strong at a fraction of the weight. Another possibility is to greatly increase the energy density of batteries—the amount of power they can hold at a given size.

So far, they can’t make enough of the nanostructured materials to cover your palm. MIT Technology Review thinks that the production breakthroughs could happen by 2020 for the initial commercialization applications.

Some recent publications:

Extreme Mechanics Letters - Ultra-strong architected Cu meso-lattices

Abstract -Ultra-strong architected Cu meso-lattices

3-dimensional solid Cu octet meso-lattices with characteristic features on the micron-scale were fabricated and mechanically tested under uniaxial compression. These architected cellular materials were fabricated by a three-step process: (1) direct laser writing of the lattice pattern into a polymer template, (2) electroplating of Cu into the template, and (3) removal of the polymer matrix. The microstructure of the electroplated Cu mainly consists of polycrystalline grains with average diameters of such that cross-sections of lattice beams mostly consist of a single grain. We discovered that the compressive yield strengths of the open-cell Cu meso-lattices can exceed the yield strength of monolithic bulk Cu as measured from a Cu thin film made with identical conditions. Meso-lattices with relative density of 0.8 had a strength of 332 MPa, which surpassed the bulk yield strength by 80%. This is diametrically opposite to predictions from structural mechanics theory, which states that strength scales linearly with relative density for the octet structure. We attribute the ability of solid Cu meso-lattices to attain such high strengths to the “smaller is stronger” size effect present in single crystalline metals with sub-micron dimensions. This work demonstrates the use and proliferation of the size-dependent strengthening unique to nanostructures in an architected structural material.

Applied Physics Letters - Ductility and work hardening in nano-sized metallic glasses

A mastery of engineered hierarchy in material microstructures might one day allow us to make ductile metallic glasses that both deform and harden like steels and possess superior strength and stiffness.

Journal of the Mechanics and Physics of Solids - The effect of size, orientation and alloying on the deformation of AZ31 nanopillars

Nextbigfuture has been covering the work since 2013

Nanometer thick walls that are made into hollow trusses to enable far lighter and stronger material.

Julia Greer's web page at Cal Tech

Journal of Materials Science - Mechanical characterization of hollow ceramic nanolattices

A talk was given at a local TEDx event, produced independently of the TED Conferences (TEDx CERN). Imagine being able to hold all the material it took to build an airplane in the palm of your hand. Julia Greer combines different design structures at varying nano-scales to create super strong and super light materials. Her research is changing the landscape of materials available today.

Julia Greer researches lightweight, 3-dimensional nano-architectures and designs experiments to assess their properties and deformation mechanisms. These ‘nano-metamaterials’ have multiple applications, which provide a rich ‘playground’ for fundamental scientific pursuits.

 

 

Abstract

In the analysis of complex, hierarchical structural meta-materials, it is critical to understand the mechanical behavior at each level of hierarchy in order to understand the bulk material response. We report the fabrication and mechanical deformation of hierarchical hollow tube lattice structures with features ranging from 10 nm to 100 μm, hereby referred to as nanolattices. Titanium nitride (TiN) nanolattices were fabricated using a combination of two-photon lithography, direct laser writing, and atomic layer deposition. The structure was composed of a series of tessellated regular octahedra attached at their vertices. In situ uniaxial compression experiments performed in combination with finite element analysis on individual unit cells revealed that the TiN was able to withstand tensile stresses of 1.75 GPa under monotonic loading and of up to 1.7 GPa under cyclic loading without failure. During the compression of the unit cell, the beams bifurcated via lateral-torsional buckling, which gave rise to a hyperelastic behavior in the load–displacement data. During the compression of the full nanolattice, the structure collapsed catastrophically at a high strength and modulus that agreed well with classical cellular solid scaling laws given the low relative density of 1.36 %. We discuss the compressive behavior and mechanical analysis of the unit cell of these hollow TiN nanolattices in the context of finite element analysis in combination with classical buckling laws, and the behavior of the full structure in the context of classical scaling laws of cellular solids coupled with enhanced nanoscale material properties.

Nature Materials - Fabrication and deformation of three-dimensional hollow ceramic nanostructures

Advanced Engineering Materials - Design and Fabrication of Hollow Rigid Nanolattices via Two-Photon Lithography

This paper presents the design and fabrication of 3-dimensional hollow metallic nanolattices using 2-photon lithography. The ability to fabricate structures of any geometry, with resolution down to 150 nm, provides opportunities to engineer structures spanning multiple length scales with potential to capitalize on combined structural and material size effects for use in many technological applications.

Nextbigfuture covered earlier publications of this work in Sept of 2013

Hawker Siddeley Harrier

From Wikipedia, the free encyclopedia

 

This article is about the first generation Harrier. For an overview of the Harrier family, see Harrier Jump Jet.

Harrier GR.1 / GR.3 AV-8A/C/S Harrier
An AV-8S Matador flies over the Spanish aircraft carrier Dédalo
Role	V/STOL ground-attack aircraft
National origin	United Kingdom
Manufacturer	Hawker Siddeley
First flight	28 December 1967 (Harrier)
Introduction	1 April 1969
Status	Retired
Primary users	Royal Air Force (historical) United States Marine Corps (historical) Spanish Navy (historical) Royal Thai Navy (historical)
Produced	1967–1970s
Number built	278[1]
Developed from	Hawker Siddeley P.1127/Kestrel
Developed into	British Aerospace Sea Harrier McDonnell Douglas AV-8B Harrier II British Aerospace Harrier II

The Hawker Siddeley Harrier, known colloquially as the "Harrier Jump Jet", was developed in the 1960s and formed the first generation of the Harrier series of aircraft. It was the first operational close-support and reconnaissance fighter aircraft with vertical/short takeoff and landing (V/STOL) capabilities and the only truly successful V/STOL design of the many that arose in that era. The Harrier was produced directly from the Hawker Siddeley Kestrel prototypes following the cancellation of a more advanced supersonic aircraft, the Hawker Siddeley P.1154. The British Royal Air Force (RAF) ordered the Harrier GR.1 and GR.3 variants in the late 1960s. It was exported to the United States as the AV-8A, for use by the US Marine Corps (USMC), in the 1970s.
The RAF positioned the bulk of their Harriers in West Germany to defend against a potential invasion of Western Europe by the Soviet Union; the unique abilities of the Harrier allowed the RAF to disperse their forces away from vulnerable airbases. The USMC used their Harriers primarily for close air support, operating from amphibious assault ships, and, if needed, forward operating bases. Harrier squadrons saw several deployments overseas. The Harrier's ability to operate with minimal ground facilities and very short runways allowed it to be used at locations unavailable to other fixed-wing aircraft. The Harrier received criticism for having a high accident rate and for a time-consuming maintenance process.
In the 1970s the British Aerospace Sea Harrier was developed from the Harrier for use by the Royal Navy (RN) on Invincible-class aircraft carriers. The Sea Harrier and the Harrier fought in the 1982 Falklands War, in which the aircraft proved to be crucial and versatile. The RN Sea Harriers provided fixed-wing air defence while the RAF Harriers focused on ground-attack missions in support of the advancing British land force. The Harrier was also extensively redesigned as the AV-8B Harrier II and British Aerospace Harrier II by the team of McDonnell Douglas and British Aerospace. The innovative Harrier family and its Rolls-Royce Pegasus engines with thrust vectoring nozzles have generated long-term interest in V/STOL aircraft. Similar V/STOL operational aircraft include the contemporary Soviet Yakovlev Yak-38. A V/STOL variant of the Lockheed Martin F-35 Lightning II is currently under development.

Contents

• 1 Development
  • 1.1 Origins
  • 1.2 Tripartite evaluation
  • 1.3 P.1154
  • 1.4 Production
• 2 Design
  • 2.1 Overview
  • 2.2 Engine
  • 2.3 Controls and handling
  • 2.4 Differences between versions
• 3 Operational history
  • 3.1 Royal Air Force
  • 3.2 United States Marine Corps
  • 3.3 Other operators
• 4 Variants
• 5 Operators
• 6 Aircraft on display
  • 6.1 Canada
  • 6.2 China
  • 6.3 Germany
  • 6.4 Poland
  • 6.5 New Zealand
  • 6.6 United Kingdom
  • 6.7 United States
• 7 Specifications (Harrier GR.3)
• 8 Popular culture
• 9 See also
• 10 References
• 11 Further reading
• 12 External links

Development

Origins

Main article: Hawker Siddeley P.1127

The Harrier's design was derived from the Hawker P.1127. Prior to developing the P.1127 Hawker Aircraft had been working on a replacement for the Hawker Hunter, the Hawker P.1121.^[2] The P.1121 was cancelled after the release of the British Government's 1957 Defence White Paper, which advocated a policy shift away from manned aircraft and towards missiles. This policy resulted in the termination of the majority of aircraft development projects then underway for the British military.^[3] Hawker sought to quickly move on to a new project and became interested in Vertical Take Off/Landing (VTOL) aircraft, which did not need runways.^{[N 1]} According to Air Chief Marshal Sir Patrick Hine this interest may have been stimulated by the presence of Air Staff Requirement 345, which sought a V/STOL ground attack fighter for the Royal Air Force.^[5]
Design work on the P.1127 was formally started in 1957 by Sir Sydney Camm, Ralph Hooper of Hawker Aircraft and Stanley Hooker (later Sir Stanley Hooker) of the Bristol Engine Company.^[6] The close cooperation between Hawker, the airframe company, and Bristol, the engine company, was viewed by project engineer Gordon Lewis as one of the key factors that allowed the development of the Harrier to continue in spite of technical obstacles and political setbacks.^[7] Rather than using rotors or a direct jet thrust, the P.1127 had an innovative vectored thrust turbofan engine, the Pegasus. The Pegasus I was rated at 9,000 pounds (40 kN) of thrust and first ran in September 1959.^[8] A contract for two development prototypes was signed in June 1960 and the first flight followed in October 1960.^[8] Of the six prototypes built three crashed—including one during an air display at the 1963 Paris Air Show.^[9]

Tripartite evaluation

Hawker Siddeley XV-6A Kestrel in later USAF markings

 

In 1961 the United Kingdom, United States and West Germany jointly agreed to purchase nine aircraft developed from the P.1127, for the evaluation of the performance and potential of V/STOL aircraft. These aircraft were built by Hawker Siddeley and were designated Kestrel FGA.1 by the UK.^[10] The Kestrel was strictly an evaluation aircraft and to save money the Pegasus 5 engine was not fully developed as intended, only having 15,000 pounds (67 kN) of thrust instead of the projected 18,200 pounds (81 kN).^[10] The Tripartite Evaluation Squadron numbered ten pilots; four each from the UK and US and two from West Germany.^[10] The Kestrel's first flight took place on 7 March 1964.^[11]
A total of 960 sorties had been made during the trials, including 1,366 takeoffs and landings, by the end of evaluations in November 1965.^[12][13] One aircraft was destroyed in an accident and six others were transferred to the United States, assigned the US designation XV-6A Kestrel, and underwent further testing.^[14][15][16] The two remaining British-based Kestrels were assigned for further trials and experimentation at RAE Bedford with one being modified to use the uprated Pegasus 6 engine.^[17]

P.1154

Main article: Hawker Siddeley P.1154

At the time of the development of the P.1127 Hawker and Bristol had also undertaken considerable development work on a supersonic version, the Hawker Siddeley P.1154, to meet a North Atlantic Treaty Organisation (NATO) requirement issued for such an aircraft.^[18] The design used a single Bristol Siddeley BS100 engine with four swivelling nozzles, in a fashion similar to the P.1127, and required the use of plenum chamber burning (PCB) to achieve supersonic speeds.^[19] The P.1154 won the competition to meet the requirement against stern competition from other aircraft manufacturers such as Dassault Aviation's Mirage IIIV. The French government did not accept the decision and withdrew; the NATO requirement was cancelled shortly after in 1965.^{[20][N 2]}
The Royal Air Force and the Royal Navy planned to develop and introduce the supersonic P.1154 independently of the cancelled NATO requirement. This ambition was complicated by the conflicting requirements between the two services—while the RAF wanted a low-level supersonic strike aircraft, the Navy sought a twin-engined air defence fighter.^[22] Following the election of the Labour Government of 1964 the P.1154 was cancelled, as the Royal Navy had already begun procurement of the McDonnell Douglas Phantom II and the RAF placed a greater importance on the BAC TSR-2's ongoing development.^[22] Work continued on elements of the project, such as a supersonic PCB-equipped Pegasus engine, with the intention of developing a future Harrier variant for the decades following cancellation.^{[23][N 3]}

AV-8C Harrier taking off from an amphibious transport dock ship

Production

Following the collapse of the P.1154's development the RAF began considering a simple upgrade of the existing subsonic Kestrel and issued Requirement ASR 384 for a V/STOL ground attack jet.^[22] Hawker Siddeley received an order for six pre-production aircraft in 1965, designated P.1127 (RAF), of which the first made its maiden flight on 31 August 1966.^[25] An order for 60 production aircraft, designated as Harrier GR.1, was received in early 1967.^[26][27] The aircraft was named after the Harrier, a small bird of prey capable of hovering, the naming following from the Hawker Siddeley Kestrel.^{[citation needed]}
The Harrier GR.1 made its first flight on 28 December 1967. It officially entered service with the RAF on 18 April 1969 when the Harrier Conversion Unit at RAF Wittering received its first aircraft.^[28] The aircraft were built in two factories—one in Kingston upon Thames, southwest London, and the other at Dunsfold Aerodrome, Surrey—and underwent initial testing at Dunsfold.^[29] The ski-jump technique for launching Harriers from Royal Navy aircraft carriers was extensively trialled at RNAS Yeovilton from 1977. Following these tests ski-jumps were added to the flight decks of all RN carriers from 1979 onwards, in preparation for the new variant for the navy, the Sea Harrier.^[30][31]
In the late 1960s the British and American governments held talks on producing Harriers in the United States. Hawker Siddeley and McDonnell Douglas formed a partnership in 1969 in preparation for American production,^[32] but Congressman Mendel Rivers and the House Appropriations Committee held that it would be cheaper to produce the AV-8A on the pre-existing production lines in the United Kingdom—hence all AV-8A Harriers were purchased from Hawker Siddeley.^[32] Improved Harrier versions with better sensors and more powerful engines were developed in later years.^[33][34][35] The USMC received 102 AV-8A and 8 TAV-8A Harriers between 1971 and 1976.^[36]

Design

Overview

The Harrier is typically used as a ground attack aircraft, though its manoeuvrability also allows it to effectively engage other aircraft at short ranges.^[37] The Harrier is powered by a single Pegasus turbofan engine mounted in the fuselage. The engine is fitted with two air intakes and four vectoring nozzles for directing the thrust generated: two for the bypass flow and two for the jet exhaust. Several smaller reaction nozzles are also fitted, in the nose, tail and wingtips, for the purpose of balancing during vertical flight.^[38] It has two landing gear units on the fuselage and two outrigger landing gear units, one on each wing tip.^[39] The Harrier is equipped with four wing and three fuselage pylons for carrying a variety of weapons and external fuel tanks.^[40]

An RAF Harrier GR.1, on loan to the USMC, displaying its underside with a full load of bombs

 

The Kestrel and the Harrier were similar in appearance, though approximately 90 per cent of the Kestrel's airframe was redesigned for the Harrier.^[41] The Harrier was powered by the more powerful Pegasus 6 engine; new air intakes with auxiliary blow-in doors were added to produce the required airflow at low speed. Its wing was modified to increase area and the landing gear was strengthened. Several hardpoints were installed, two under each wing and one underneath the fuselage; two 30 mm (1.2 in) ADEN cannon gun pods could also be fitted to the aircraft's underside. The Harrier was outfitted with updated avionics to replace the basic systems used in the Kestrel;^{[N 4]} a navigational-attack system incorporating an inertial navigation system, originally for the P.1154, was installed and information was presented to the pilot by a head-up display and a moving map display.^[43][44]
The Harrier's VTOL abilities allowed it to be deployed from very small prepared clearings or helipads as well as normal airfields.^{[N 5]} It was believed that, in a high-intensity conflict, air bases would be vulnerable and likely to be quickly knocked out.^{[N 6]} The capability to scatter Harrier squadrons to dozens of small "alert pads" on the front lines was highly prized by military strategists and the USMC procured the aircraft because of this ability.^{[47][N 7]} Hawker Siddeley noted that STOL operation provided additional benefits over VTOL operation, saving fuel and allowing the aircraft to carry more ordnance.^[49]

"I still don't believe the Harrier. Think of the millions that have been spent on VTO in America and Russia, and quite a bit in Europe, and yet the only vertical take-off aircraft which you can call a success is the Harrier. When I saw the Harrier hovering and flying backwards under control, I reckoned I'd seen everything. And it's not difficult to fly." -Thomas Sopwith^[50]

The Harrier, while serving for many decades in various forms, has been criticised on multiple issues; in particular a high accident rate, though Nordeen notes that several conventional single-engine strike aircraft like the Douglas A-4 Skyhawk and LTV A-7 Corsair II had worse accident rates.^[51] The Los Angeles Times reported in 2003 that the Harrier "...has amassed the highest major accident rate of any military plane now in service. Forty-five Marines have died in 148 noncombat accidents".^[52] Colonel Lee Buland of the USMC declared the maintenance of a Harrier to be a "challenge"; the need to remove the wings before performing most work upon the engine, including engine replacements, meant the Harrier required considerable man-hours in maintenance, more than most aircraft. Buland noted however that the maintenance difficulties were unavoidable in order to create a V/STOL aircraft.^[53]

Engine

Main article: Rolls-Royce Pegasus

Rolls-Royce Pegasus engine on display, sections have been cut out to provide an internal view

 

The Pegasus turbofan jet engine, developed in tandem with the P.1127 then the Harrier, was designed specifically for V/STOL manoeuvring. Bristol Siddeley developed it from their earlier conventional Orpheus turbofan engine, the main difference being the thrust generated is directed through four rotatable nozzles.^[54] The engine is equipped for water injection to increase thrust and takeoff performance in hot and high altitude conditions; in normal V/STOL operations the system would be used in landing vertically with a heavy weapons load.^[55] The water injection function had originally been added following the input of US Air Force Colonel Bill Chapman, who worked for the Mutual Weapons Development Team.^[56] Water injection was necessary in order to generate maximum thrust, if only for a limited time, and was typically used during landing, especially in high ambient temperatures.^[53]
The aircraft was initially powered by the Pegasus 6 engine which was replaced by the more powerful Pegasus 11 during the Harrier GR.1 to GR.3 upgrade process.^[57] The primary focus throughout the engine's development was on achieving high performance with as little weight as possible,^[57] tempered by the amount of funding that was available.^[10] Following the Harrier's entry to service the focus switched to improving reliability and extending engine life;^[55] a formal joint US–UK Pegasus Support Program operated for many years and spent a £3-million annual budget to develop engine improvements.^[57] Several variants have been released; the latest is the Pegasus 11–61 (Mk 107), which provides 23,800 lbf (106 kN) thrust, more than any previous engine.^[58]

Controls and handling

Thrust vectoring nozzle on a Sea Harrier

Locations of the four nozzles on the aircraft

The Harrier has been described by pilots as "unforgiving".^[59] The aircraft is capable of both forward flight (where it behaves in the manner of a typical fixed-wing aircraft above its stall speed), as well as VTOL and STOL manoeuvres (where the traditional lift and control surfaces are useless) requiring skills and technical knowledge usually associated with helicopters. Most services demand great aptitude and extensive training for Harrier pilots, as well as experience in piloting both types of aircraft. Trainee pilots are often drawn from highly experienced and skilled helicopter pilots.^{[N 8][11]}
In addition to normal flight controls, the Harrier has a lever for controlling the direction of the four vectoring nozzles. It is viewed by senior RAF officers as a significant design success, that to enable and control the aircraft's vertical flight required only a single lever added in the cockpit.^[60] For horizontal flight, the nozzles are directed rearwards by shifting the lever to the forward position; for short or vertical takeoffs and landings, the lever is pulled back to point the nozzles downwards.^[61][62]
The Harrier has two control elements not found in conventional fixed-wing aircraft: the thrust vector and the reaction control system. The thrust vector refers to the slant of the four engine nozzles and can be set between 0° (horizontal, pointing directly backwards) and 98° (pointing down and slightly forwards). The 90° vector is normally deployed for VTOL manoeuvring. The reaction control is achieved by manipulating the control stick and is similar in action to the cyclic control of a helicopter. While irrelevant during forward flight mode, these controls are essential during VTOL and STOL manoeuvres.^[63]
The wind direction is a critical factor in VTOL manoeuvres. The procedure for vertical takeoff involves facing the aircraft into the wind. The thrust vector is set to 90° and the throttle is brought up to maximum, at which point the aircraft leaves the ground. The throttle is trimmed until a hover state is achieved at the desired altitude.^[49] The short-takeoff procedure involves proceeding with normal takeoff and then applying a thrust vector (less than 90°) at a runway speed below normal takeoff speed; usually the point of application is around 65 knots (120 km/h). For lower takeoff speeds the thrust vector is greater.^[60] The reaction control system involves a series of thrusters at key points in the aircraft's fuselage and nose, also the wingtips. Thrust from the engine can be temporarily syphoned to control and correct the aircraft's pitch and roll during vertical flight.^[64]
Rotating the vectored thrust nozzles into a forward-facing position during normal flight is called vectoring in forward flight, or "VIFFing". This is a dog-fighting tactic, allowing for sudden braking and higher turn rates than would normally be possible for an aircraft with such a short wingspan. Braking could cause a chasing aircraft to overshoot and present itself as a target for the Harrier it was chasing, a combat technique formally developed by the USMC for the Harrier in the early 1970s.^[65][66]
Although a transonic design, compared to most other combat aircraft the Harrier is unusual in having greater engine thrust than weight, as a result, in conventional flight, the aircraft has excellent acceleration and rate of climb.^{[citation needed]}

Differences between versions

The two largest users of the Harrier were the Royal Air Force and the United States Marine Corps (USMC). The exported model of the aircraft operated by the USMC was designated the AV-8A Harrier, which was broadly similar to the RAF's Harrier GR.1.^[67] Changes included the removal of all magnesium components, which corroded quickly at sea, and the integration of American radios and Identification Friend or Foe (IFF) systems; furthermore the outer pylons, unlike the RAF aircraft, were designed from delivery to be equipped with self-defence AIM-9 Sidewinder heat-seeking air-to-air missiles.^[36] Most of the AV-8As had been delivered with the more powerful Pegasus engine used in the GR.3 instead of the one used in the earlier GR.1.^[67] Two-seat Harriers were operated for training purposes; the body was stretched and a taller tail fin added.^[68] The RAF trained in the T.2 and T.4 versions, while T.4N and T.8 were training versions the Navy's Sea Harrier, with appropriate fittings.^[69] The US and Spain flew the TAV-8A and TAV-8S, respectively.^[70][71]
All RAF GR.1s and the initial AV-8As were fitted with the Ferranti FE541 inertial navigation/attack suite, but these were replaced in the USMC Harriers by a simpler Interface/Weapon Aiming Computer to aid quick turnaround between missions. The Martin-Baker ejection seats were also replaced by the Stencel SEU-3A in the American aircraft.^[72][73] The RAF had their GR.1 aircraft upgraded to the GR.3 standard, which featured improved sensors, a nose-mounted laser tracker, the integration of electronic countermeasure (ECM) systems and a further upgraded Pegasus Mk 103.^[33][34] The USMC upgraded their AV-8As to the AV-8C configuration; this programme involved the installation of ECM equipment and adding a new inertial navigation system to the aircraft's avionics. Substantial changes were the Lift Improvement Devices, to increase VTOL performance; at the same time several airframe components were restored or replaced to extend the life of the aircraft.^[35] Spain's Harriers, designated AV-8S or VA.1 Matador for the single-seater and TAV-8S or VAE.1 for the two-seater, were almost identical to USMC Harriers differing only in the radios fitted.^[74]
The Royal Navy's Fleet Air Arm (FAA) operated a substantially modified variant of the Harrier, the British Aerospace Sea Harrier. The Sea Harrier was not intended for ground-attack duties and, unlike the standard Harrier, was equipped with radar and Sidewinder missiles for air combat duties and fleet air defence.^{[N 9]} The Sea Harrier was also fitted with navigational aids for carrier landings, modifications to reduce corrosion and a raised bubble-canopy for greater visibility.^[75][76] The aircraft were later equipped to use AIM-120 AMRAAM beyond-visual-range anti-aircraft missiles and the more advanced Blue Vixen radar for longer range air-to-air combat, as well as Sea Eagle missiles for conducting anti-ship missions.^[77]
The McDonnell Douglas AV-8B Harrier II is the latest Harrier variant, a second-generation series to replace the first generation of Harrier jets already in service; all the above variants of the Harrier have mainly been retired with the Harrier II taking their place in the RAF, USMC and FAA. In the 1970s the United Kingdom considered two options for replacing their existing Harriers: joining McDonnell Douglas (MDD) in developing the BAE Harrier II, or the independent development of a "Big Wing" Harrier. This proposal would have increased the wing area from 200 to 250 square feet (19 to 23 m²), allowing for significant increases in weapons load and internal fuel reserves.^[78] The option of cooperation with MDD was chosen in 1982 over the more risky isolated approach.^[79]

Operational history

Royal Air Force

The first RAF squadron to be equipped with the Harrier GR.1, No. 1 Squadron, started to convert to the aircraft at RAF Wittering in April 1969.^[22][80] An early demonstration of the Harrier's capabilities was the participation of two aircraft in the Daily Mail Transatlantic Air Race in May 1969, flying between St Pancras railway station, London and downtown Manhattan with the use of aerial refuelling. The Harrier completed the journey in 6 hours 11 minutes.^[81][82] Two Harrier squadrons were established in 1970 at the RAF's air base in Wildenrath to be part of its air force in Germany; another squadron was formed there two years later. In 1977, these three squadrons were moved forward to the air base at Gütersloh, closer to the prospective front line in the event of an outbreak of a European war. One of the squadrons was disbanded and its aircraft distributed between the other two.^[83]

A No. 1453 Flight Harrier GR.3 at Stanley Airport in 1984

 

In RAF service, the Harrier was used in close air support (CAS), reconnaissance, and other ground-attack roles. The flexibility of the Harrier led to a long-term heavy deployment in West Germany as a conventional deterrent and potential strike weapon against Soviet aggression; from camouflaged rough bases the Harrier was expected to launch attacks on advancing armour columns from East Germany.^[84] Harriers were also deployed to bases in Norway and Belize, a former British colony.^[84] No. 1 Squadron was specifically earmarked for Norwegian operations in the event of war, operating as part of Allied Forces Northern Europe. The Harrier's capabilities were necessary in the Belize deployment, as it was the only RAF combat aircraft capable of safely operating from the airport's short runway;^[85] British forces had been stationed in Belize for several years due to tensions over a Guatemalan claim to Belizean territory; the forces were withdrawn in 1993, two years after Guatemala recognized the independence of Belize.^[86]
In the Falklands War in 1982, 10 Harrier GR.3s of No. 1 Squadron operated from the aircraft carrier HMS Hermes.^[87] As the RAF Harrier GR.3 had not been designed for naval service, the 10 aircraft had to be rapidly modified prior to the departure of the task force. Special sealants against corrosion were applied and a new deck-based inertial guidance aid was devised to allow the RAF Harrier to land on a carrier as easily as the Sea Harrier.^[88] Transponders to guide aircraft back to the carriers during night-time operations were also installed, along with flares and chaff dispensers.^[89]
As there was little space on the carriers, two requisitioned merchant container ships, the Atlantic Conveyor and Atlantic Causeway, were modified with temporary flight decks and used to carry Harriers and helicopters to the South Atlantic.^[90] The Harrier GR.3s focused on providing close air support to the ground forces on the Falklands and attacking Argentine positions; suppressing enemy artillery was often a high priority.^[91][92] Sea Harriers were also used in the war, primarily conducting fleet air defence and combat air patrols against the threat of attacking Argentine fighters.^[90] However, both Sea Harriers and Harrier GR.3s were used in ground-attack missions against the main airfield and runway at Stanley.^[93]
If most of the Sea Harriers had been lost, the GR.3s would have replaced them in air patrol duties, even though the Harrier GR.3 was not designed for air defence operations; as such the GR.3s quickly had their outboard weapons pylons modified to take air-to-air Sidewinder missiles.^[88] From 10 to 24 May 1982, prior to British forces landing in the Falklands, a detachment of three GR.3s provided air defence for Ascension Island until three F-4 Phantom IIs arrived to take on this responsibility.^[94] During the Falklands War, the greatest threats to the Harriers were deemed to be surface-to-air missiles (SAMs) and small arms fire from the ground.^[95] In total, four Harrier GR.3s and six Sea Harriers were lost to ground fire, accidents, or mechanical failure.^[96] More than 2,000 Harrier sorties were conducted during the conflict—equivalent to six sorties per day per aircraft.^[97]

An RAF Harrier GR.3 in Belize, 1990

 

Following the Falklands war, British Aerospace explored the Skyhook, a new technique to operate Harriers from smaller ships. Skyhook would have allowed the launching and landing of Harriers from smaller ships by holding the aircraft in midair by a crane; secondary cranes were to hold weapons for rapid re-arming. This would potentially have saved fuel and allowed for operations in rougher seas.^[98] The system was marketed to foreign customers,^{[N 10]} and it was speculated that Skyhook could be applied to large submarines such as the Russian Typhoon class, but the system attracted no interest.^[100]
The first generation of Harriers did not see further combat with the RAF after the Falklands War, although they continued to serve for years afterwards. As a deterrent against further Argentine invasion attempts, No. 1453 Flight RAF was deployed to the Falkland Islands from August 1983 to June 1985.^[101] However the second generation Harrier IIs saw action in Bosnia, Iraq, and Afghanistan. The first generation Hawker Siddeley airframes were replaced by the improved Harrier II, which had been developed jointly between McDonnell Douglas and British Aerospace.^[102]

United States Marine Corps

"In my mind the AV-8A Harrier was like the helicopter in Korea. [It] had limited capability, but that's how the first-generation automobile, boat, or other major systems evolved... it brought us into the world of flexible basing and the Marine Corps into the concept of vertical development"

Major General Joe Anderson.^[103]

The United States Marine Corps began showing a significant interest in the aircraft around the time the first RAF Harrier squadron was established in 1969, and this motivated Hawker Siddeley to further develop the aircraft to encourage a purchase.^[104] Although there were concerns in Congress about multiple coinciding projects in the close air support role,^{[N 11]} the Marine Corps were enthusiastic about the Harrier and managed to overcome efforts to obstruct its procurement.^[106]
The AV-8A entered service with the Marine Corps in 1971, replacing other aircraft in the Marines' attack squadrons.^[107] The service became interested in performing ship-borne operations with the Harrier. Admiral Elmo Zumwalt promoted the concept of a Sea Control Ship, a 15,000-ton light carrier equipped with Harriers and helicopters, to supplement the larger aircraft carriers of the US Navy. An amphibious assault ship, the USS Guam, was converted into the Interim Sea Control Ship and operated as such between 1971 and 1973 with the purpose of studying the limits and possible obstacles for operating such a vessel.^[108][109] Since then the Sea Control Ship concept has been subject to periodic re-examinations and studies, often in the light of budget cuts and questions over the use of supercarriers.^{[110][111][N 12]}

A pair of USMC AV-8A from VMA-513 in formation flight in 1974.

 

Other exercises were performed to demonstrate the AV-8A's suitability for operating from various amphibious assault ships and aircraft carriers, including a deployment of 14 Harriers aboard USS Franklin D. Roosevelt for six months in 1976.^[108] The tests showed, amongst other things, that the Harrier was capable of performing in weather where conventional carrier aircraft could not.^[108] In support of naval operations, the USMC devised and studied several methods to further integrate the Harrier. One result was Arapaho, a stand-by system to rapidly convert civilian cargo ships into seagoing platforms for operating and maintaining a handful of Harriers, to be used to augment the number of available ships to deploy upon.^{[113][N 13]}
When the reactivation of the Iowa-class battleships was under consideration, a radical design for a battleship-carrier hybrid emerged that would have replaced the ship's rear turret with a flight deck, complete with a hangar and two ski jumps, for operating several Harriers. However, the USMC considered the need for naval gunfire support to be a greater priority than additional platforms for carrier operations, while the cost and delay associated with such elaborate conversions was significant, and the concept was dropped.^[114][115]
The Marines Corps' concept for deploying the Harriers in a land-based expeditionary role focused on aggressive speed. Harrier forward bases and light maintenance facilities were to be set up in under 24 hours on any prospective battle area. The forward bases, containing one to four aircraft, were to be located 20 miles (32 km) from the forward edge of battle (FEBA), while a more established permanent airbase would be located around 50 miles (80 km) from the FEBA.^{[116][N 14]} The close proximity of forward bases allowed for a far greater sortie rate and reduced fuel consumption.^[116]

A pair of USMC AV-8A Harriers refuelling from a Lockheed Martin KC-130 tanker

 

The AV-8A's abilities in air-to-air combat were tested by the Marine Corps by conducting mock dogfights with McDonnell Douglas F-4 Phantom IIs; these exercises trained pilots to use the vectoring-in-forward-flight (VIFF) capability to outmanoeuvre their opponents and showed that the Harriers could act as effective air-to-air fighters at close range.^[65] The success of Harrier operations countered scepticism of V/STOL aircraft, which had been judged to be expensive failures in the past.^[117] Marine Corps officers became convinced of the military advantages of the Harrier and pursued extensive development of the aircraft.^[118]
Starting in 1979 the USMC began upgrading their AV-8As to the AV-8C configuration—the work focused mainly on extending useful service lives and improving VTOL performance.^[35] The AV-8C and the remaining AV-8A Harriers were retired by 1987.^[119] These were replaced by the Harrier II, designated as the AV-8B, which was introduced into service in 1985.^[120] The performance of the Harrier in USMC service led to calls for the United States Air Force to procure Harrier IIs in addition to the USMC's own plans,^[116] but these never resulted in Air Force orders. Since the late 1990s, the AV-8B has been slated to be replaced by the F-35B variant of the Lockheed Martin F-35 Lightning II, a more modern V/STOL jet aircraft.^[121]

Other operators

A Spanish Navy AV-8S Matador aircraft

 

Due to the Harrier's unique characteristics it attracted a large amount of interest from other nations, often as attempts to make their own V/STOL jets were unsuccessful, such as in the cases of the American XV-4 Hummingbird and the German VFW VAK 191B.^{[N 15]} Operations by the USMC aboard the USS Nassau in 1981 and by British Harriers and Sea Harriers in the Falklands War proved that the aircraft were highly effective in combat. These operations also demonstrated that "Harrier Carriers" provided a powerful presence at sea without the expense of big deck carriers.^{[122][N 16]}
Following the display of Harrier operations from small carriers, the navies of Spain and later Thailand bought the Harrier for use as their main carrier-based fixed-wing aircraft.^{[N 17]} Spain's purchase of Harriers was complicated by long-standing political friction between the British and Spanish governments of the era; even though the Harriers were manufactured in the UK they were sold to Spain with the US acting as an intermediary.^[126] Since 1976, the Spanish Navy operated the AV-8S Matador from their aircraft carrier Dédalo (formerly the USS Cabot); the aircraft provided both air defence and strike capabilities for the Spanish fleet.^[127] Spain later purchased five Harriers directly from the British government to replace losses.^[128]

Stern view of HTMS Chakri Naruebet, with a single Harrier on deck.

 

Hawker Siddeley aggressively marketed the Harrier for export. At one point the company was holding talks with Australia, Brazil, Switzerland, India and Japan. Of these only India became a customer, purchasing the Sea Harrier.^[129] At one point China came very close to becoming an operator of the first generation Harrier. Following an overture by the UK in the early 1970s, when relations with the West were warming, China became interested in the aircraft as it sought to modernise its armed forces; British Prime Minister James Callaghan noted significant hostility from the USSR over the sales bid.^[130][131] The deal was later cancelled by the UK as part of a diplomatic backlash after China invaded Vietnam in 1979.^[132]
The Spanish Navy, Thai Navy, Royal Air Force, and United States Marine Corps have all retired their first-generation Harriers. Spain sold seven single-seat and two twin-seat Harriers to Thailand in 1998.^{[128][133][N 18]} The Royal Thai Navy's AV-8S Matadors were delivered as part of the air wing deployed on the new light aircraft carrier HTMS Chakri Naruebet.^[135] The Thai Navy had from the start significant logistical problems keeping the Harriers operational due to a shortage of funds for spare parts and equipment, leaving only a few Harriers serviceable at a time. In 1999, two years after being delivered, only one airframe was in airworthy condition.^[136][137] Around 2003, Thailand considered acquiring former Royal Navy Sea Harriers, which were more suitable for maritime operations and better equipped for air defence, to replace their AV-8S Harriers; this investigation did not progress to a purchase.^[138] The last first-generation Harriers were retired by Thailand in 2006.^[139]

Variants

Main article: List of Harrier variants

A Royal Air Force Harrier GR.3 aircraft parked on the flight line during Air Fete '84 at RAF Mildenhall.

A USMC TAV-8A Harrier from VMAT-203 on the flight line

Harrier GR.1, GR.1A, GR.3 

Single-seat versions for the RAF.^{[33][34][140]} The RAF ordered 118 of the GR.1/GR.3 series,^[141] with the last production aircraft delivery in December 1986.^[142] 122 built.^[1]

AV-8A, AV-8C Harrier 

Single-seat versions for the US Marine Corps.^[67] The USMC ordered 102 AV-8As (company designation: Harrier Mk. 50).^[141] The AV-8C was an upgrade to the AV-8A.^[35] 110 built.^[1]

AV-8S Matador 

Export version of the AV-8A Harrier for the Spanish Navy, who designated them as VA-1 Matador.^[71] 10 built.^[1]

Harrier T.2, T.2A, T.4, T.4A

Two-seat training versions for the RAF, with a stretched body and taller tail fin.^[68] 25 built.^[1]

Harrier T.4N, T.8, T.60

Two-seat training versions for the Royal Navy and Indian Navy, avionics fittings based on the Sea Harrier.^[69]

TAV-8A Harrier  

Two-seat training version for the USMC, powered by a Pegasus Mk 103.^[70]

TAV-8S Matador 

Two-seat training version for the Spanish Navy and later sold to the Royal Thai Navy.^[71]

Operators

Main article: List of Harrier operators

 Thailand

• Royal Thai Navy

 India

• Indian Navy

United States Marine Corps AV-8A of VMA-231 in 1980

 Spain

• Spanish Navy

 United Kingdom

• Royal Air Force
• Royal Navy

 United States

• United States Marine Corps

Aircraft on display

Former Harrier GR.1 that crashed in 1971 and used as a static engine test bed by Rolls-Royce, seen on display at the Bristol Aero Collection, Kemble, England

Canada

AV-8A

• 158966 - Canada Aviation and Space Museum, Ottawa, Ontario.^[143]

China

GR.3

• XZ965 - Beijing Aviation Museum, Beijing, China. In 1996, the Chinese used a La-11 to exchange for a Harrier GR.3.^{[citation needed]}

Germany

GR.1

• XV278 - Luftwaffenmuseum der Bundeswehr, Gatow.^[144]

GR.3

• XZ998 - Flugausstellung Leo Junior at Hermeskeil.^[145]

Poland

GR.3

• XW919 - Polish Aviation Museum, Kraków, Poland.^[146]

New Zealand

GR.3

• XZ129 - Ashburton Aviation Museum, Ashburton, New Zealand.^[147]

United Kingdom

GR.1

• XV277 - National Museum of Flight, East Fortune.^[148]

GR.3

• XV744 - Tangmere Military Aviation Museum, Chichester, West Sussex.^[149]
• XV748 - Yorkshire Air Museum, Elvington.^[150]
• XV751 - Gatwick Aviation Museum, Surrey.^[151]
• XV752 - Bletchley Park, Buckinghamshire.^[152]
• XV779 - RAF Wittering (Gate Guardian).^[153]
• XZ133 - Imperial War Museum, Duxford.^[154]
• XZ968 - Muckleburgh Collection, Norfolk.^[155]
• XZ997 - RAF Museum, Hendon.^[156]

Mk.52 G-VTOL

• ZA250 - Brooklands Museum, Surrey.^[157]

T.4

• XW934 - Farnborough Air Sciences Trust, Farnborough, Hampshire.^[158]

United States

AV-8A

• 158976 - Cherry Point MCAS, North Carolina.^[159]

TAV-8A

• 159381 - Oakland Aviation Museum, Oakland, California.^[160]

AV-8C

• 158387 - Flying Leatherneck Aviation Museum, Marine Corps Air Station Miramar, San Diego, California.^[161]
• 158710 - Quonset Air Museum, North Kingstown, Rhode Island.^[162]
• 158975 - National Naval Aviation Museum, NAS Pensacola, Pensacola, Florida.^[163]
• 158977 - Museum of Flight, Seattle, Washington.^[164]
• 159232 - Intrepid Sea, Air & Space Museum, New York City, New York.^[165]
• 159241 - Pima Air & Space Museum, Tucson, Arizona.^[166]

Specifications (Harrier GR.3)

Data from Jane's All The World's Aircraft 1988–89^[167]

General characteristics

• Crew: One
• Length: 46 ft 10 in (14.27 m)
• Wingspan: 25 ft 3 in (7.70 m)
• Height: 11 ft 11 in (3.63 m)
• Wing area: 201.1 ft² (18.68 m²)
• Empty weight: 13,535 lb (6,140 kg)
• Max. takeoff weight: 25,200 lb (11,430 kg)
• Powerplant: 1 × Rolls-Royce Pegasus 103 turbofan with four swivelling nozzles, 21,500 lbf (95.6 kN) Four vertical flight puffer jets use engine bleed air, mounted in the nose, wingtips, and tail.

Performance

• Maximum speed: 730 mph (635 knots, 1,176 km/h) at sea level
• Combat radius: 230 mi (200 nmi, 370 km) lo-lo-lo with 4,400 lb (2,000 kg) payload
• Ferry range: 2,129 mi (1,850 nmi, 3,425 km)
• Endurance: 1 hr 30 min (combat air patrol – 115 mi (185 km) from base)
• Service ceiling: 51,200 ft (15,600 m)
• Time to climb to 40,000 ft (12,200 m): 2 min 23 s

Armament

• Guns: 2× 30 mm (1.18 in) ADEN cannon pods under the fuselage
• Hardpoints: 4× under-wing & 1× under-fuselage pylon stations with a capacity of 5,000 lb (2,268 kg) and provisions to carry combinations of:
  • Rockets: 4× Matra rocket pods with 18× SNEB 68 mm rockets each
  • Missiles: 2× AIM-9 Sidewinders Air-to-air missiles
  • Bombs: A variety of unguided iron bombs, BL755 cluster bombs or laser-guided bombs
  • Others:
    • 1× Reconnaissance pod
    • 2× drop tanks for extended range/loitering time

Popular culture

Main article: Hawker Siddeley Harrier in fiction

See also

	Royal Air Force portal
	Aviation portal

• Aircraft in fiction#Harrier family

Aircraft of comparable role, configuration and era

• Rockwell XFV-12
• Yakovlev Yak-38